The present invention relates generally to energetic materials, and more particularly relates to novel chemical compounds useful, inter alia, as high energy oxidizing agents. Methods for using the novel compounds as oxidizing agents in energetic compositions are also provided, as are energetic compositions containing the compounds. In addition, the invention relates to use of the present compounds as pharmaceutical agents, e.g., as vasodilating agents.
xe2x80x9cEnergeticxe2x80x9d compounds are used extensively in a wide variety of applications, e.g., in explosive formulations, propellants, gas-generating compositions, and the like. It is generally preferred that such materials have a high energy content yet be relatively insensitive to impact, such that accidents are avoided and energy is released only when intended. The requirements of insensitivity and high energy are in conflict, making the development of new energetic materials a difficult and challenging synthetic problem.
In developing new energetic compounds, a number of factors come into play. For example, heats of formation, density, melting and decomposition temperatures, carbon content and, generally, nitrogen content, are properties which must be considered. Energetic compounds should display good thermal and shock properties, have high heats of formation, and be straightforward to synthesize in bulk. It is generally preferred that an energetic compound have a melting point above about 100xc2x0 C., an exothermic heat of combustion and a positive heat of formation xcex94Hf, and a high decomposition temperature, with a relatively large separation between melting point and decomposition temperature preferred such that an energetic composition may be melt cast from the selected compound. Finally, it is of course preferred that an energetic compound be relatively simple and straightforward to synthesize in high yield.
A number of energetic compounds are known as useful as oxidizers, explosives and the like. Energetic compounds have also been disclosed as useful to inflate automobile and aircraft occupant restraint bags. However, previously known materials are generally limited in one or more ways, e.g., they are overly impact-sensitive, difficult to synthesize on a large scale, not sufficiently energetic, or the like. In addition, energetic compositions used to inflate occupant restraint bags in automobiles and aircraft typically contain potentially toxic heavy metal igniter materials, e.g., mercury compounds, Pb(N3)2 or the like.
The present invention provides a new class of compounds which overcomes the aforementioned limitations in the art. The energetic compounds to which the invention pertains are commonly referred to as xe2x80x9csecondaryxe2x80x9d explosives, i.e., compounds whose energy is released after activation by initiator compounds, also termed xe2x80x9cprimaryxe2x80x9d explosives. The compounds now provided herein meet all of the above-mentioned criteria, and outperform conventional energetic compounds in a number of ways. For example, higher O2 density is provided than obtained with conventional secondary explosives such as ammonium perchlorate. In addition, the novel compounds are highly energetic while not overly impact-sensitive, and are straightforward to synthesize in high yield.
In addition, the compounds of the invention undergo denitration in the body, releasing nitric oxide (NO); the compounds may accordingly be used as pharmaceutical agents, i.e., as so-called xe2x80x9cNO-donors.xe2x80x9d NO donors are useful as vasodilating agents, insofar as NO activates guanylyl cyclase, increasing intracellular levels of cyclic guanosine 3xe2x80x2,5xe2x80x2-monophosphate (cGMP), and cGMP brings about smooth muscle relaxation. Previously known NO donors include, for example, nitroglycerin (glyceryl trinitrate), isosorbide dinitrate, isosorbide-5-mononitrate, erythrityl tetranitrate, pentaerythritol tetranitrate, sodium nitroprusside, S-nitroso-N-acetylpenicillamine (SNAP), linsidomine chlorohydrate (also known as SIN-1), and the so-called xe2x80x9cNONOates,xe2x80x9d complexes of nitric oxide and nucleophiles that contain the N2O2-group and release NO upon heating or hydrolysis without need for activation. The pharmacological application of many known NO donors is limited, however, as a result of unwanted side effects, an undesirable NO release profile, or the like. Thus, there is a continuing need in the art for improved pharmaceutical agents useful as vasodilators.
It is accordingly an object of the invention to address the above-mentioned need in the art by providing novel compounds that are useful as energetic materials, e.g., as high energy oxidizing agents.
It is another object of the invention to provide methods for using the novel compounds as high energy oxidizing agents.
It is still another object of the invention to provide energetic compositions containing one or more of the novel compounds.
It is yet another object of the invention to provide such energetic compositions in the form of propellant formulations, explosive compositions, and the like.
It is a further object of the invention to provide gas-generating compositions containing one or more of the novel compounds.
It is still a further object of the invention to provide methods and compositions for using a compound of the invention as a pharmaceutical agent.
Additional objects, advantages and novel features of the invention will be set forth in part in the description which follows, and in part will become apparent to those skilled in the art upon examination of the following, or may be learned by practice of the invention.
In a first embodiment, the invention relates to novel compounds of formula (I) 
wherein:
R is either (a) C1-C24 hydrocarbyl, optionally substituted with one or more substituents and optionally containing one or more non-hydrocarbyl linkages, e.g., xe2x80x94Oxe2x80x94, xe2x80x94Sxe2x80x94, xe2x80x94NHxe2x80x94, xe2x80x94N(alkyl)xe2x80x94, xe2x80x94N(NO2)xe2x80x94, xe2x80x94C(O)xe2x80x94, or xe2x80x94C(O)Oxe2x80x94, and optionally containing one or more non-hydrogen, noncarbon atoms, e.g., S, Si, B, Al, or the like, (b) xe2x80x94Lxe2x80x94R1, where L and R1 are as defined below, or (c) polymeric;
L comprises a divalent hydrocarbylene linking group;
R1 is aromatic, nitrogen-containing heterocyclic, xe2x80x94ONR2R3, xe2x80x94Oxe2x80x94[NR2R3R4]+Yxe2x88x92,xe2x80x94ONxe2x95x90CR5R6 or xe2x80x94Oxe2x80x94[Nxe2x95x90CR5R6]H+Yxe2x88x92 wherein R2, R3 and R4 are independently hydrogen, alkyl, aryl or aralkyl, if alkyl, aryl or aralkyl, optionally substituted with xe2x80x94NO2, xe2x80x94NH2 and/or xe2x80x94NF2 substituents, or wherein R2 and R3 are linked to provide an optionally substituted cyclic moiety, Yxe2x88x92 is an oxidizing anion or a nitrogen-containing heterocyclic anion, and R5 and R6 are independently H, xe2x80x94NH2, xe2x80x94NF2, xe2x80x94NR7xe2x80x94NH2 or xe2x80x94NR7(NO2) wherein R7 is hydrogen, alkyl, aryl or aralkyl, if alkyl, aryl or aralkyl, optionally substituted with xe2x80x94NO2, xe2x80x94NH2 and/or xe2x80x94NF2 substituents, or R5 and R6 can be linked together to form an optionally substituted cycloalkyl ring; and
n is an integer indicating the number of xe2x80x94N(NO2)xe2x80x94Lxe2x80x94R1 groups bound to R and is thus in the range of 1 to nmax wherein nmax is the maximum number of substituents that can be bound to R through single covalent bonds.
In another embodiment of the invention, energetic compositions are provided containing one or more of the novel compounds as secondary explosives. These energetic compositions may take any number of forms and have a variety of uses, such as in rocket propellant formulations, including both solid and solution propellants, in liquid monopropellants, in bipropellant and tripropellant compositions, in pyrotechnics, firearms, and the like. In addition, the compounds of the invention are useful in energetic, gas-generating compositions for inflating automotive or aircraft occupant restraint devices. As will be appreciated by those skilled in the art, the aforementioned uses are exemplary in nature and not intended to represent a comprehensive list of possibilities.
In an additional embodiment of the invention, the novel compounds are used as pharmaceutical agents. That is, the compounds of the invention are useful as NO donors and, accordingly, as vasodilators. Methods are thus provided which comprise administration of a compound of the invention to a human or animal, to bring about any effect for which a vasodilator would be useful, e.g., to treat hypertension, angina pectoris, peripheral vascular disease, vasculogenic impotence, and the like. Generally, the compound is administered in a pharmaceutical composition containing a pharmacologically acceptable carrier and, optionally, one or more additional active agents. The compounds may also be useful in increasing the permeability of the so-called xe2x80x9cblood-brain barrierxe2x80x9d to therapeutic agents.
Before the present compounds, compositions and methods are disclosed and described, it is to be understood that this invention is not limited to specific molecular structures, ligands, or the like, as such may vary. It is also to be understood that the terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting.
It must be noted that, as used in the specification and the appended claims, the singular forms xe2x80x9ca,xe2x80x9d xe2x80x9canxe2x80x9d and xe2x80x9cthexe2x80x9d include plural referents unless the context clearly dictates otherwise. Thus, for example, reference to xe2x80x9ca compound of the inventionxe2x80x9d includes combinations of two or more compounds of the invention, reference to xe2x80x9ca secondary explosivexe2x80x9d includes combinations of secondary explosives, etc. Similarly, reference to xe2x80x9ca nitro groupxe2x80x9d as in a compound substituted with xe2x80x9ca nitro groupxe2x80x9d includes the possibility of substitution with more than one nitro group, reference to xe2x80x9csubstituentxe2x80x9d includes one or more substituents, and the like.
The term xe2x80x9calkylxe2x80x9d as used herein refers to a branched or unbranched saturated hydrocarbon group of 1 to 24 carbon atoms, such as methyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, t-butyl, octyl, decyl, tetradecyl, hexadecyl, eicosyl, tetracosyl and the like, as well as cycloalkyl groups such as cyclopentyl, cyclohexyl and the like. The term xe2x80x9clower alkylxe2x80x9d intends an alkyl group of 1 to 6 carbon atoms, preferably 1 to 4 carbon atoms.
The term xe2x80x9calkylenexe2x80x9d as used herein refers to a difunctional saturated branched or unbranched hydrocarbon chain containing from 1 to 24 carbon atoms, and includes, for example, methylene (xe2x80x94CH2xe2x80x94), ethylene (xe2x80x94CH2xe2x80x94CH2xe2x80x94), propylene (xe2x80x94CH2xe2x80x94CH2xe2x80x94CH2xe2x80x94), 2-methylpropylene (xe2x80x94CH2xe2x80x94CH(CH3)xe2x80x94CH2xe2x80x94), hexylene (xe2x80x94(CH2)6xe2x80x94), and the like. xe2x80x9cLower alkylenexe2x80x9d refers to an alkylene group of 1 to 6, more preferably 1 to 4, carbon atoms.
The term xe2x80x9calkenylxe2x80x9d as used herein refers to a branched or unbranched hydrocarbon group of 2 to 24 carbon atoms containing at least one carbonxe2x80x94carbon double bond, such as ethenyl, n-propenyl, isopropenyl, n-butenyl, isobutenyl, t-butenyl, octenyl, decenyl, tetradecenyl, hexadecenyl, eicosenyl, tetracosenyl and the like. Preferred alkenyl groups herein contain 2 to 12 carbon atoms and 1 to 3 carbonxe2x80x94carbon double bonds. The term xe2x80x9clower alkenylxe2x80x9d intends an alkenyl group of 2 to 6 carbon atoms, preferably 2 to 4 carbon atoms, containing one xe2x80x94Cxe2x95x90Cxe2x80x94 bond. The term xe2x80x9ccycloalkenylxe2x80x9d intends a cyclic alkenyl group of 3 to 8, preferably 5 or 6, carbon atoms.
The term xe2x80x9calkenylenexe2x80x9d refers to a difunctional branched or unbranched hydrocarbon chain containing from 2 to 24 carbon atoms and at least one carbonxe2x80x94carbon double bond. xe2x80x9cLower alkenylenexe2x80x9d refers to an alkenylene group of 2 to 6, more preferably 2 to 5, carbon atoms, containing one xe2x80x94Cxe2x95x90Cxe2x80x94 bond.
The term xe2x80x9calkynylxe2x80x9d as used herein refers to a branched or unbranched hydrocarbon group of 2 to 24 carbon atoms containing at least one carbonxe2x80x94carbon triple bond, such as ethynyl, n-propynyl, isopropynyl, n-butynyl, isobutynyl, t-butynyl, octynyl, decynyl and the like. Preferred alkynyl groups herein contain 2 to 12 carbon atoms. The term xe2x80x9clower alkynylxe2x80x9d intends an alkynyl group of 2 to 6, preferably 2 to 4, carbon atoms, and one carbonxe2x80x94carbon triple bond.
The term xe2x80x9calkynylenexe2x80x9d refers to a difunctional branched or unbranched hydrocarbon chain containing from 2 to 24 carbon atoms and at least one carbonxe2x80x94carbon triple bond. xe2x80x9cLower alkynylenexe2x80x9d refers to an alkynylene group of 2 to 6, more preferably 2 to 5, carbon atoms, containing one carbonxe2x80x94carbon triple bond.
The term xe2x80x9carylxe2x80x9d as used herein refers to an aromatic species containing 1 to 3 aromatic rings, either fused or linked, and either unsubstituted or substituted with 1 or more substituents typically selected from the group consisting of nitro, amino (including primary amino, lower alkyl substituted secondary and tertiary amino, and halogenated amino such as xe2x80x94NF2), halogen and lower alkyl, where x is an integer in the range of 0 to 6 inclusive as outlined above. Preferred aryl substituents contain 1 aromatic ring or 2 fused aromatic rings. The term xe2x80x9caralkylxe2x80x9d intends a moiety containing both alkyl and aryl species, and will usually be used to refer to aryl-substituted alkyl groups. The term xe2x80x9caralkylenexe2x80x9d will be used in a similar manner to refer to moieties containing both alkylene and aryl species, typically intending aryl-substituted alkylene.
The term xe2x80x9carylenexe2x80x9d refers to a difunctional aromatic moiety; xe2x80x9cmonocyclic arylenexe2x80x9d refers to a cyclopentylene or phenylene group. These groups may be substituted with up to four ring substituents as outlined above.
The term xe2x80x9cheterocyclicxe2x80x9d refers to a five- or six-membered monocyclic structure or an eight- to eleven-membered bicyclic heterocycle. Generally, although not necessarily, the heterocyclic substituents herein are aromatic. Each heterocycle consists of carbon atoms and from one to four heteroatoms selected from the group consisting of nitrogen, oxygen and sulfur, with the proviso that the heterocycle contains at least one nitrogen atom. Preferred heterocyclic groups are five-membered rings containing one to four nitrogen atoms, and thus include pyrrole, pyrazole, imidazole, 1,2,3-triazole, 1,2,4-triazole and tetrazole, with 1,2,4-triazole and tetrazole particularly preferred.
xe2x80x9cHaloxe2x80x9d or xe2x80x9chalogenxe2x80x9d refers to fluoro, chloro, bromo or iodo, and usually relates to halo substitution for a hydrogen atom in an organic compound. Of the halos, chloro and fluoro are generally preferred.
xe2x80x9cHydrocarbylxe2x80x9d refers to unsubstituted and substituted hydrocarbon radicals containing 1 to about 20 carbon atoms, including linear and branched, saturated and unsaturated species, such as alkyl groups, alkenyl groups, aryl groups, and the like. The term xe2x80x9clower hydrocarbylxe2x80x9d refers to a hydrocarbyl radical containing 1 to about 6 carbon atoms.
xe2x80x9cHydrocarbylenexe2x80x9d refers to a difunctional hydrocarbyl radical, where xe2x80x9chydrocarbylxe2x80x9d is as defined above.
The term xe2x80x9cpolymerxe2x80x9d is used in its conventional sense to refer to a compound comprised of two or more monomer units, and is intended to include homopolymers as well as copolymers, and oligomers (typically comprised of at most 20 monomer units) as well as higher molecular weight polymeric entities.
xe2x80x9cOptionalxe2x80x9d or xe2x80x9coptionallyxe2x80x9d means that the subsequently described event or circumstance may or may not occur, and that the description includes instances where said event or circumstance occurs and instances where it does not. For example, the phrase xe2x80x9coptionally substitutedxe2x80x9d aromatic ring means that the aromatic ring may or may not be substituted and that the description includes both an unsubstituted aromatic ring and an aromatic ring bearing one or more substituents.
The term xe2x80x9cenergeticxe2x80x9d to describe the various compounds disclosed and claimed herein is used to refer to a material having a high energy content as represented by an exothermic (negative) heat of combustion. Preferably, the energetic compounds herein also have a positive heat of formation xcex94Hf.
As used herein all reference to the Periodic Table of the Elements and groups thereof is to the version of the table published by the Handbook of Chemistry and Physics, CRC Press, 1995, which uses the IUPAC system for naming groups.
The compounds of the invention are represented by structural formula (I) 
wherein R, L, R1 and n are as defined earlier herein.
That is, R is either (a) C1xe2x80x94C24 hydrocarbyl, optionally substituted with one or more, typically one to six, substituents and optionally containing one or more, typically one to six, non-hydrocarbyl linkages, e.g., xe2x80x94Oxe2x80x94, xe2x80x94Sxe2x80x94, xe2x80x94NHxe2x80x94, xe2x80x94N(alkyl)xe2x80x94, xe2x80x94N(NO2)xe2x80x94, xe2x80x94C(O)xe2x80x94, xe2x80x94C(O)Oxe2x80x94, xe2x80x94Oxe2x80x94xe2x80x94Oxe2x80x94, xe2x80x94Nxe2x95x90Nxe2x80x94 or 
and optionally containing one or more nonhydrogen, noncarbon atoms, e.g., S, Si, B or Al, (b) xe2x80x94Lxe2x80x94R1, or (c) polymeric;
L comprises a divalent hydrocarbylene linking group;
R1 is aromatic, nitrogen-containing heterocyclic, xe2x80x94ONR2R3, xe2x80x94Oxe2x80x94[NR2R3R4]+Yxe2x88x92, xe2x80x94ONxe2x95x90CR5R6 or xe2x80x94Oxe2x80x94[Nxe2x95x90CR5R6]H+Yxe2x88x92 wherein R2, R3 and R4 are independently hydrogen, alkyl, aryl or aralkyl, if alkyl, aryl or aralkyl, optionally substituted with xe2x80x94NO2, xe2x80x94NH2 and/or xe2x80x94NF2 substituents, or wherein R2 and R3 are linked to provide an optionally substituted cyclic moiety, typically a three- to six-membered ring optionally containing one or more heteroatoms selected from the group consisting of N, O and S and optionally substituted with xe2x80x94NO2, xe2x80x94NH2, xe2x80x94NF2 and/or other substituents, Yxe2x88x92 is an oxidizing anion or a nitrogen-containing heterocyclic anion, and R5 and R6 are independently H, xe2x80x94NH2, xe2x80x94NF2, xe2x80x94NR7xe2x80x94NH2 or xe2x80x94NR7(NO2) wherein R7 is hydrogen, alkyl, hydrocarbyl aryl or aralkyl, if alkyl, aryl or aralkyl, optionally substituted with xe2x80x94NO2, xe2x80x94NH2 and/or xe2x80x94NF2 substituents, or R5 or R6 can be linked together to form an optionally substituted three- to six-membered cyclic moiety; and
n is an integer defining the number of xe2x80x94N(NO2)xe2x80x94Lxe2x80x94R1 groups bound to R, and thus is in the range of 1 to nmax, wherein nmax is the maximum number of substituents that can be bound to R through single, covalent bonds.
Examples of R radicals include, but are not limited to, carbyl, methylene, methyl, ethylene, ethyl, ethenylene, ethenyl, ethynylene, ethynyl, trimethylene, propylene, n-propyl, isopropyl, 1-propynyl, 2-propynyl, cyclopropyl, 1,2,3-propanetriyl, allyl, tetramethylene, n-butyl, 1,3-butadienyl, 1-butenyl, 2-butenyl, 3-butenyl, 2-butenylene, cyclobutyl, pentamethylene, 1-pentenylene, pentyl, pentenyl, cyclopentyl, cyclopentenyl, cyclopentylene, cyclohexyl, cyclohexenyl, cyclohexylene, cyclohexenylene, hexyl, hexamethylene, heptyl, octyl, 1,1,3,3-tetramethylbutyl, nonyl, nonylene, decyl, decylene, undecyl, undecylene, cetyl, octadecanoyl, phenyl, phenylene, phenylenedimethylene, phenethyl, phenylethylene, xylylene, benzyhydryl, biphenyl, biphenylyl, naphthyl, naphthylene, napthylmethylidene, pyranyl, pyrrolidinyl, morpholino, thiazolyl, tetracosyl, xe2x80x94CH2xe2x80x94Oxe2x80x94CH2xe2x80x94, xe2x80x94CH2xe2x80x94Sxe2x80x94CH2xe2x80x94, and the like. R may be unsubstituted or substituted, if substituted, generally having 1 to 6, more typically 1 to 3, substituents such as lower alkyl, lower alkenyl, lower alkynyl, amino, lower alkyl-substituted amino, di(lower alkyl) amino, nitro, halo, halogenated lower alkyl, halogenated amino (e.g., NF2), xe2x80x94NR7 (NO2) wherein R7 is as defined previously, or the like; R may also be substituted with one or more xe2x80x94Lxe2x80x94R1 moieties. Preferred R radicals are C1-C6 hydrocarbyl groups, e.g., carbyl, methylene, ethylene, ethenylene, dimethylethylene, propylene, etc., and xe2x80x94Lxe2x80x94R1.
R, as noted above, may also be polymeric, such that the xe2x80x94N(NO2)xe2x80x94Lxe2x80x94R1 groups are pendant to a polymer backbone. The polymer backbone may comprise a polyolefin such as polyethylene, polypropylene or polyisoprene, a halogenated polymer such as polytrifluoroethylene, poly(vinyl fluoride) or poly(vinylidene chloride), a cellulosic polymer such as ethyl cellulose or hydroxypropyl cellulose, a nitrogenous polymer such as polyethyleneimine, a polyamine or a polyamide, or a polyglycol such as polyoxymethylene or poly(ethylene oxide). The xe2x80x94N(NO2)xe2x80x94Lxe2x80x94R1 groups are preferably introduced prior to polymerization, i.e., they are present on the monomeric species used to create the polymer. For example, poly(ethylene oxide) having xe2x80x94N(NO2)xe2x80x94Lxe2x80x94R1 pendant groups may be prepared by ring-opening polymerization of the substituted epoxide 
and, similarly, polyethylene having pendant xe2x80x94N(NO2)xe2x80x94Lxe2x80x94R1 groups may be prepared by addition polymerization of the substituted olefin 
Alternatively, pendant xe2x80x94N(NO2)xe2x80x94Lxe2x80x94R1 groups may be introduced into an intact polymer by reaction with functional groups present therein, e.g., xe2x80x94CH2Cl, xe2x80x94CH2NH2 or the like.
L may be, for example, alkylene, alkenylene, alkynylene, typically lower alkylene, lower alkenylene or lower alkynylene, arylene, alkarylene, aralkylene, optionally substituted with amino, nitro, lower alkyl and/or halogen substituents and/or containing xe2x80x94Oxe2x80x94. xe2x80x94Sxe2x80x94, xe2x80x94N(alkyl)xe2x80x94, etc. As long as xe2x80x9cLxe2x80x9d inserts at least one atom between the N-nitro group and xe2x80x94R1 to provide spacing therebetween, and as long as there are no electron-withdrawing groups alpha to the oxygen atom bound to the N-nitro linkage, there are no limitations on the identity of L, and L may be any of the bifunctional substituents listed above as xe2x80x9cRxe2x80x9d groups. However, typical linking groups suitable as xe2x80x9cLxe2x80x9d are lower alkylene, lower alkenylene, including cyclic lower alkylene and cyclic lower alkenylene, and monocyclic arylene, including monocyclic aromatic heterocycles, e.g., methylene, ethylene, n-propylene, ethenylene, tetramethylene, cyclohexylene, phenylene, etc.
Specific R1 groups include, but are not limited to, xe2x80x94ONH2, xe2x80x94ON(CH3)2, xe2x80x94ONH(CH3), xe2x80x94ONH(CH2CH3), xe2x80x94ONH(CH(CH3)2), xe2x80x94ONxe2x95x90C(NH2)2, xe2x80x94ONxe2x95x90C(NF2)2, xe2x80x94ONxe2x95x90C(NHxe2x80x94NH2)2, xe2x80x94ONxe2x95x90C(H)NH2, xe2x80x94ONxe2x95x90C(H)xe2x80x94NHxe2x80x94NH2,xe2x80x94ONxe2x95x90C(NH2)xe2x80x94NHxe2x80x94NH2, xe2x80x94ONxe2x95x90C(H)NHxe2x80x94CH(NH2)2, xe2x80x94ONxe2x95x90C(NH2)(NHNO2), xe2x80x94ONH3+Yxe2x88x92, xe2x80x94ON(CH3)3+Yxe2x88x92, xe2x80x94ON(CH2CH3)3+Y31 , xe2x80x94Oxe2x80x94[Nxe2x95x90C(NH2)2 xc2x7H+]Yxe2x88x92, xe2x80x94Oxe2x80x94[Nxe2x95x90C(NF2)2xc2x7H+]Yxe2x88x92, xe2x80x94Oxe2x80x94[Nxe2x95x90C(NHxe2x80x94NH2)2xc2x7H+]Yxe2x88x92, xe2x80x94Oxe2x80x94[Nxe2x95x90C(H)NH2xc2x7H+]Yxe2x88x92, xe2x80x94Oxe2x80x94[Nxe2x95x90C(H)xe2x80x94NHxe2x80x94NH2xc2x7H+]Yxe2x88x92, xe2x80x94Oxe2x80x94[Nxe2x95x90C(NH2)xe2x80x94NHxe2x80x94NH2xc2x7H+]Yxe2x88x92, xe2x80x94Oxe2x80x94[Nxe2x95x90C(H)NHxe2x80x94CH(NH2)2xc2x7H+]Yxe2x88x92 and xe2x80x94Oxe2x80x94[Nxe2x95x90C(NH2)xc2x7(NHNO2)H+]Yxe2x88x92, wherein Yxe2x88x92 is any anion useful to provide oxidizing capability in an energetic composition, including NOxe2x88x923, NOxe2x88x922, chlorate, perchlorate, hexafluorophosphate, N(NO2)2xe2x88x92, C(NO2xe2x88x92)3xe2x88x92, halogen anions, heterocyclic anions such as the anion of 3,5-dinitro-1,2,4-triazole, and the like.
Other R1 groups may be represented as 
wherein: p is 1 or 2; q is 1 or 2; r is zero or 1; R8, R9, R10 and R11 are independently hydrogen, lower alkyl, lower alkenyl, lower alkynyl, amino, lower alkyl-substituted amino, di(lower alkyl)amino, nitro, halo, halogenated lower alkyl, halogenated amino, xe2x80x94NR7(NO2), etc., with hydrogen, xe2x80x94NO2, xe2x80x94NH2 and xe2x80x94NF2 preferred; and R12 is CR13R14, NR14, O or S, preferably CR13R14 or NR14 wherein R13 and R14 are as defined for R8, R9, R10 and R11, and most preferably CH2, CH(NO2), C(NO2)2, Nxe2x80x94NO2 or Nxe2x80x94NH2. Examples of such R1 groups include, but are not limited to, 
wherein these R1 moieties may be electrostatically neutral, as shown, or carry a positive charge, in which case there will be an association with an anion Yxe2x88x92 as described above.
Additional R1 groups comprise nitrogen-containing heterocycles, preferably monocyclic five-membered nitrogen-containing heterocycles or bicyclic nitrogen-containing heterocycles comprised of two five-membered rings or one five-membered ring and one six-membered ring, optionally substituted with one through four substituents per ring, wherein the substituents are selected from the group consisting of amino, alkylamino, dialkylamino, halogenated amino, nitro, alkyl and halogen. Suitable five-membered nitrogen-containing heterocycles include, for example, moieties having the structure 
wherein R15, R16, R17 and R18 are independently selected from the group consisting of N, Nxe2x86x92O, (N+xe2x80x94Ra)Yxe2x88x92, CH, Cxe2x80x94Rb, Cxe2x80x94NRcRd, and Cxe2x80x94NO2 in which Ra and Rb are independently C1-C24 alkyl or fluoro, Rc and Rd are independently H or C1-C24 alkyl, and Yxe2x88x92 is a counterion as defined previously. Preferably, Ra and Rb are lower alkyl, and Rc and Rd are independently either H or lower alkyl. Particularly preferred R15, R16, R17 and R18 groups are N, CH and Cxe2x80x94NO2.
Suitable bicyclic nitrogen-containing heterocycles include, but are not limited to, moieties having the structure 
wherein R15, R16, R17 and R18 are as defined previously, R19, R20, R21, and R22 are as defined for R15, R16, R17 and R18, and x is zero or 1. Other suitable bicyclic nitrogen-containing heterocycles have the structure 
wherein R15, R16 and R18 are as defined previously, R23, R24, R25 and R26 are as defined for R15, R16, R17 and R18, J is C or N, and L is as defined with regard to earlier structures herein.
Particularly preferred nitrogen-containing heterocycles include pyrrole, pyrazole, imidazole, 1,2,3-triazole, 1,2,4-triazole, tetrazole, indazole, quinazoline, and the like, either unsubstituted or substituted on a ring carbon and/or nitrogen with a substituent such as amino, nitro, lower alkyl or halogen, although substitution on one or two ring carbon atoms with a nitro substituent is most preferred.
The integer xe2x80x9cnxe2x80x9d in formula (I) indicating the number of xe2x80x94N(NO2)xe2x80x94Lxe2x80x94R1 groups that are bound to R, is at least 1, but may be 2, 3, . . . and up to nmax, wherein nmax indicates the maximum number of substituents that can be bound to R through single covalent bonds. For example, when R is xe2x80x94Lxe2x80x94R1, nmax is 1 and n is 1. When R is xe2x80x94CH3, nmax is 1 and n is 1. When R is C, nmax is 4 and n is 1, 2, 3 or 4. When R is xe2x80x94CHxe2x95x90CHxe2x80x94, nmax is 2 and n can be 1 or 2. In the latter two cases, obviously R will have to have nmax-n substituents that are not shown, which will generally be hydrogen, alkyl, amino, alkyl-substituted amino, including mono-substituted alkylamino and dialkylamino, halogenated amino, or alkyl substituted with amino, halogenated amino, nitro, or other nitrogen-containing groups; typically, the remaining (nmax-n) substituents are hydrogen, lower alkyl, amino, lower alkyl(amino), di(lower alkyl) amino, or nitro-substituted lower alkyl.
Representative compounds encompassed by generic structure (I) are as follows: 
Gas-generating compositions for inflating airbags or for other uses contain a compound of the invention as discussed earlier herein, an igniter material, and, optionally, an additional oxidizer. xe2x80x9cIgniter materials,xe2x80x9d as appreciated by those skilled in the art, are compounds that act as primary explosives in an energetic composition. Preferred igniter compounds for use herein are thermally stable, typically up to a temperature of at least about 150xc2x0 C.; the compounds should also have a relatively high heat of formation, and be safe, economical and straightforward to synthesize in relatively high yield. Conventional igniters such as lead azide and lead styphnate may be used, although preferred igniters are the N,Nxe2x80x2-azobis-nitroazoles described in commonly assigned U.S. Pat. No. 5,889,161 to Bottaro et al. for xe2x80x9cN,N-Azobis-Nitroazoles and Analogs Thereof as Igniter Compounds for Use in Energetic Compositions.xe2x80x9d Examples of additional oxidizers that may be incorporated into the present gas-generating compositions include, but are not limited to, ammonium nitrate (AN), phase-stabilized ammonium nitrate (PSAN), ammonium dinitramide (AND), potassium nitrate (KN), potassium dinitramide (KDN), sodium peroxide (Na2O2), ammonium perchlorate (AP), and KDN-AN, a cocrystallized form of potassium dinitramide and ammonium nitrate.
The aforementioned gas-generating compositions may also, if desired, contain a gas-generating fuel and a binder. Suitable gas-generating fuels include triaminoguanidine nitrate (TAGN), diaminoguanidine nitrate (DAGN), monoaminoguanidine nitrate (MAGN), 3-nitro-1,2,4-triazole-5-one (NTO), salts of NTO, urazole, triazoles, tetrazoles, guanidine nitrate, oxamide, oxalyldihydrazide, melamine, various pyrimidines, semicarbazide (H2Nxe2x80x94(CO)xe2x80x94NHNH2), azodicarbonamide (H2Nxe2x80x94(CO)xe2x80x94Nxe2x95x90Nxe2x80x94(CO)xe2x80x94NH2), and mixtures thereof. Suitable binders are generally organic polymeric materials, e.g., polycarbonates, polyesters, polyurethanes and the like.
Another area of interest is in the manufacture of rocket propellant compositions, including solid and solution propellants, typically solid propellants. Such compositions will contain, in addition to a secondary explosive comprising a compound of the invention and an igniter material, a binder and fuel. Examples of binder materials for use in propellant applications include but are not limited to polyoxetanes, polyglycidyl azide, hydroxyl-terminated polybutadiene, polybutadiene-acrylonitrileacrylic acid terpolymer, polyethers, polyglycidyl nitrate, and polycaprolactone; see, e.g., U.S. Pat. No. 5,292,387 to Highsmith et al. Suitable propellant fuels will generally be metallic, e.g., aluminum, beryllium, boron, magnesium, zirconium, or mixtures or alloys thereof. Other components for incorporation into propellant compositions include plasticizers, bum rate modifiers, ballistic additives, and the like.
The present compounds may also be used as the liquid oxidizer component of bipropellant and tripropellant compositions, without need for additional oxidizing agents. In addition, the compounds are useful in pyrotechnic applications, in firearms, and the like. If desired, the compounds of the invention may be combined with other secondary explosives, including, but not limited to, 2,4,6-trinitrotoluene (TNT), cyclo-1,3,5-tri-methylene-2,4,6-trinitramine (RDX or cyclonite), high melting explosives (HMX), and picric acid.
The compounds of the invention are also useful as pharmaceutical agents. In one embodiment, methods and compositions for treating NO-responsive disorders and conditions in a human or animal are provided. That is, the compounds of the invention, by virtue of the N-nitro group, undergo denitration in the body and are for that reason useful as NO donors and thus as vasodilating agents.
The invention thus encompasses methods for using the novel compounds as vasodilators, e.g., in treating moderate to severe hypertension, in providing acute relief of angina pectoris, for long-term prophylactic management of angina pectoris, to produce controlled hypotension during surgical procedures, for the treatment of ischemic pain, to treat pulmonary edema associated with acute myocardial infarction, to treat or prevent vasculogenic impotence, to treat peripheral vascular disease, to treat esophageal disorders such as achalasia and esophageal spasm, to facilitate endoscopic removal of gallstones, and in obstetrics, e.g., in inducing uterine relaxation to prolong pregnancy and manage premature labor.
The compounds may be administered via the oral, parenteral (including subcutaneous, intravenous and intramuscular injection), nasal, buccal, sublingual, urethral, rectal, vaginal, cutaneous, or transdermal routes, and the composition and carrier are to be selected accordingly. For compounds of the invention that are orally active, oral administration is preferred. The amount of compound administered will, of course, be dependent on the indication, the subject being treated, the subject""s weight, the mode of administration, and the judgment of the prescribing physician. Typically, however, dosage will be at most 10% of the LD50 for any one compound, and will generally be in the range of approximately 0.01 mg/kg/day to 2.0 mg/kg/day, preferably in the range of about 0.1 mg/kg/day to 1.0 mg/kg/day. Suitable dosages will generally be analogous to dosages employed for known nitrovasodilators such as nitroglycerin, sodium nitroprusside, isosorbide dinitrate, and the like.
The compounds will generally be administered in a pharmaceutical composition containing an effective amount of the active compound and a pharmacologically acceptable excipient suited to the particular mode of administration. The compositions may also include other pharmaceutical agents, adjuvants, diluents, buffers, etc. Depending on the intended mode of administration, the pharmaceutical compositions may be in the form of solid, semi-solid or liquid dosage forms, such as, for example, tablets, suppositories, pills, capsules, powders, liquids, suspensions, or the like, preferably in unit dosage form suitable for single administration of a precise dosage.
The compounds also find pharmaceutical utility in increasing the permeability of the xe2x80x9cblood-brain barrierxe2x80x9d to therapeutic agents. While not unambiguously defined in anatomical terms, the blood-brain barrier is accepted as a boundary between the periphery and the central nervous system (CNS), serving as a barrier to the passive diffusion of substances from the bloodstream into various regions of the CNS. There is an ongoing need for compounds that increase permeability of the blood-brain barrier to enhance the efficacy of various drugs, e.g., chemotherapeutic agents or the like, that are used to treat infectious or tumors localized in the brain. The present compounds are useful in this regard.
The compounds of the invention may be readily synthesized in a variety of ways using techniques that are relatively straightforward and readily scaled up. Representative synthetic methods are described in Examples 1 through 5 below.
Synthetic details not explicitly disclosed will be within the knowledge of or may readily deduced by those skilled in the art of synthetic organic chemistry, or may be found in the relevant texts such as Kirk-Othmer""s Encyclopedia of Chemical Technology, House""s Modern Synthetic Reactions, C. S. Marvel and G. S. Hiers"" text, ORGANIC SYNTHESIS, Collective Volume 1, or in T. L. Gilchrist, Heterocyclic Chemistry, 2nd Ed. (New York: John Wiley and Sons, 1992) or the like. Synthesis of representative compounds is exemplified below.
Manufacture of gas-generating compositions, propellants and other energetic compositions may be carried out using conventional means, as will be appreciated by those skilled in the art. A suitable method for preparing anhydrous gas-generating composition is disclosed, for example, in U.S. Pat. No. 5,473,647 to Blau et al. and in international patent publication WO 95/00462 (Poole et al.). Of course, other methods for manufacture may be used as well. Such methods are described in the pertinent literature or will be known to those familiar with the preparation of energetic compositions.
It is to be understood that while the invention has been described in conjunction with the preferred specific embodiments thereof, that the foregoing description as well as the examples which follow are intended to illustrate and not limit the scope of the invention. Other aspects, advantages and modifications within the scope of the invention will be apparent to those skilled in the art to which the invention pertains.
All patents, patent applications, and publications mentioned herein are hereby incorporated by reference in their entirety.
The following examples are put forth so as to provide those of ordinary skill in the art with a complete disclosure and description of how to prepare and use the compounds disclosed and claimed herein. Efforts have been made to ensure accuracy with respect to numbers (eg., amounts, temperature, etc.) but some errors and deviations should be accounted for. Unless indicated otherwise, parts are parts by weight, temperature is in xc2x0 C. and pressure is at or near atmospheric.